1. Field of the Invention
The present invention relates to active matrix display apparatuses typified by an active matrix liquid crystal display apparatus, and to a related display method.
2. Description of Related Art
In a conventional active matrix display apparatus, switching thin-film transistors or nonlinear elements, which are provided for respective pixels that are arranged in matrix form, control charges entering or exiting from pixel electrodes.
The active matrix liquid crystal display apparatus generally employs a display method in which one frame is divided into a first field and a second field. FIG. 1A shows a timing chart of this method. First, information is written to rows of pixels that are arranged in the form of an m-row/n-column matrix as shown in FIG. 7, and the written information is displayed as a first field. Then, next information is written again to same rows of the pixels and the written information is displayed as a second field. The first and second fields thus formed constitute one frame.
More specifically, in the matrix region of FIG. 7, information is sequentially written to first-row pixels (1, 1), (2, 1), (3, 1), . . . , then to second-row pixels (1, 2), (2, 2), (3, 2), . . . , and so forth to form a first field. Next, following information is sequentially written again to first-row pixels (1, 1), (2, 1), (3, 1), . . . , then to second-row pixels (1, 2), (2, 2), (3, 2), . . . , and so forth to form a second field. One frame is formed when information writing to all pixels two times has been completed. Display continues as frames are formed 30 times per second.
One reason or employing the above display method is to make a flicker, which is likely to occur with a bright picture, less recognizable. A flicker is more easily recognized when the vertical scanning period is longer. Therefore, a flicker can be made less recognizable by halving the apparent vertical scanning period by constituting one frame of two fields.
Another reason for employing the above display method is to reduce the amount of information necessary for one frame.
However, the above display method has a problem of decrease in vertical resolution because the number of scanning lines is substantially reduced to n/2.
In particular, in a large-screen projection type display method as employed in a projector, non-display fields are recognized by a viewer This is a major factor of decreasing the vertical resolution.
An object of the present invention is to provide a display apparatus and method in which the vertical resolution does not decrease even with the above-described scanning method.
According to one aspect of the invention, there is provided a display method in which information is written to a matrix-like pixel region, comprising the steps of:
writing information to odd rows in a first field;
writing information to even rows in a second field, starting at a time point when the writing of the first field has been completed; and
holding the information written in the first field until completion of the writing of the second field.
In this display method, as shown in FIG. 1B, a first field is formed by writing information to Nth rows where N represent odd rows 1, 3, 5, . . . and a second field is formed by writing information to (N+1)th rows. The first and second fields are related to each other such that the writing of the second field is started at a time point when the writing of the first field has been completed, while information written in the first field is held until completion of the writing of the second field.
Further, a first field of the next frame is started at a time point when the writing of the second field has completed, while information written in the second field is held. By repeating this operation, high resolution can be attained in the vertical scanning direction.
According to another aspect of the invention, there is provided a display method in which information is written to a matrix-like pixel region, comprising the steps of:
writing information to Nth rows in a first field, where N represents odd or even numbers;
writing information to (N+1)th rows in a second field, starting at a time point when the writing of the first field has been completed; and
holding the information written in the first field until completion of the writing of the second field.
The invention can be applied to three-dimensional display, time-divisional display of different images, and other types of display in addition to ordinary two-dimensional display. The matrix-like structure includes a matrix circuit of an active matrix liquid crystal display apparatus and a matrix circuit of a display apparatus using an EL device.
According to a further aspect of the invention, there is provided a display apparatus comprising:
means for projecting two divisional images onto a projection surface so that the two divisional images are superimposed on each other, an image formed on the projection surface being constituted of pixels that are arranged in matrix form;
means for forming Nth rows on the projection surface by using one of the two divisional images, where N represent odd numbers 1, 3, 5, . . . , and
means for forming (N+1)th rows on the projection surface by using the other divisional image.
FIGS. 5A to 5C show a specific example of this display apparatus. In this display apparatus, six images formed by six respective active matrix regions shown in FIG. 6 are grouped into two images, which are projected onto a screen 510 through an optical system 508 so as to be superimposed on each other.
The display apparatus of FIGS. 5A to SC has an integrated liquid crystal panel 507 shown in FIG. 6. For example, in the integrated liquid crystal panel 507, active matrix regions 701 to 703 form the Nth rows as mentioned above and active matrix regions 704 to 706 form the (N+1)th rows.
According to another aspect of the invention, there is provided a display apparatus for performing display in which one frame consists of a first field and a second field, comprising:
image forming means for forming the first field; and
image forming means for forming the second field.
The operation of this display apparatus is specifically illustrated in FIG. 1B. As shown in FIG. 1B, active matrix regions 701 to 703 (see FIG. 6) form a first field and active matrix regions 704 to 706 form a second field.
In particular, as shown in FIG. 1B, at a time point when information is written (i.e., an image is displayed) by one of the image forming means in a period of the first field. Upon completion of this information writing, image formation of the second field by the other image forming means is started. The image of the first field is maintained during the writing of the second field. As a result, the apparent vertical resolution can be kept high.
According to another aspect of the invention, there is provided a display method in which information is written to respective pixels of a displayed image that are arranged in matrix form, comprising the steps of:
projecting two divisional images onto a projection surface so that the two divisional images are combined on the projection surface;
forming Nth rows on the projection surface by using one of the two divisional images, where N represent odd numbers 1, 3, 5, . . . ; and
forming (N+1)th rows on the projection surface by using the other divisional image.
According to still another aspect of the invention, there is provided a display method in which one frame consists of a first field and a second field, wherein the first field and the second field are formed by separate image forming devices.
In operation, as shown in FIG. 1B, a first field for scanning of odd fields and a second field for scanning of even rows are related to each other such that even if writing of the first field is finished, a state at a time point of completion of the writing of the first field is maintained (i.e., information written in the first field is maintained) until completion of writing of the second field. Writing of a first field of the next frame is started upon completion of the writing of the second field.
By virtue of coexistence of information written in the first field; and information written in the second field, the number of apparent scanning lines can be doubled as compared to the conventional method, that is, the vertical resolution can be kept high.